1. Field of the Invention
The present invention is related to the field of signal transmission.
2. Related Art
As a result of recent developments in digital signal processing technologies, the use of digital interfaces is now becoming a major trend in signal transmission. Standards for digital interfaces, such as IEEE1394, allow various formatted digital signals to be transmitted through a single digital interface.
More specifically, using the IEEE1394 digital interface, digital audio/video devices are connected with each other to form a network of the devices. Digitized audio/video signals are mostly coded or compressed into particular formats, and then transmitted through the digital interface. Such a digital interface allows the digital signals, no matter what format they are in, to be transmitted within the network, and does not regulate or control the connections of devices through which the digital signals are being transmitted.
In order to accomplish signal transmission between two devices in a network, one of which transmits a digital signal and the other of which receives the digital signal, the receiving device must be capable of decoding the signal transmitted in a particular format. In other words, both the transmitting and receiving devices have to have a common feature with regard to their coding/decoding capabilities.
It could have been relatively easy to fulfill this requirement when digital signals were coded and transmitted in limited number of formats such as the Digital Video (DV) format. The situation has changed, however. Various types of compression techniques, including Digital Video Interactive (DVI) and Motion Picture Experts Group (MPEG) compression, have been developed and used to achieve higher performance of digital signal transmission. In addition, some of these formats have distinctive modes, such as High Definition (HD) and Standard Definition (SD) modes of MPEG2, in terms of the transmission speed and bandwidth of the signal.
In theory, if every device in a network were to have a common feature with regard to their coding/decoding capabilities, digital signals would be transmitted between the devices through the IEEE1394 digital interface. In practice, however, each device has limited coding/decoding capabilities. As a result, the coding/decoding capabilities of the transmitting and receiving devices may not necessarily correspond to each other.
When such a discrepancy in digital signal formats occurs, it is possible to accomplish signal transmission between the devices in the network by                using a converter which converts a digital signal format into another format that the receiving device can cope with; or        decoding a digital signal into analog so that the signal is supplied in an analog format.        
To do so, a connection between devices in the network has to be reestablished so that it involves an appropriate decoder or converter. It is, however, a complicated task to reestablish a pertinent connection taking into account both the format of the signal that a transmitting device provides and the various capabilities of the devices.
Furthermore, an analog interface has to be used to transmit a signal in an analog format; otherwise the analog signal cannot be transmitted successfully. In other words, a determination needs to be made as to which interface is to be used, digital or analog, depending upon the format of the signal transmitted through the interface.
For the foregoing reasons, there is a need for a method and apparatus for controlling connections between a transmitting device and a receiving device based on the capabilities of the devices within a network.